After Effects, but inside a browser tab (free, no install)

AtomCut is a free motion design and video studio that runs in a browser tab. If you know After Effects, you already know most of it: compositions, keyframes, a graph editor, expressions, tracking, rigs, 3D. The difference is where it lives. You open a URL and start keyframing. No installer, no account, no Creative Cloud updater asking to restart.

This post maps the After Effects workflow onto AtomCut, tool by tool, with screenshots from the editor as it is today (version 4.17). It also lists where After Effects is still the better choice, because there are real ones.

A tracker on the cabin (97% confidence across the clip), and a label riding it. The green strip under the clip on the timeline is the tracked span.

What does each After Effects tool map to?

In After Effects	In AtomCut	Notes
Composition, precomp	Frame, nested comp	Frames sit side by side on an infinite canvas, like artboards in Figma. Nest one inside another and it plays as a clip.
Graph Editor	Curves panel	Speed and value curves, eased handles, every keyed property in one view.
Hold keyframe	Hold easing	Drawn as a step in Curves, and kept as a hold in Lottie.
Expressions	Expressions in any field	Type wiggle(2, 10) or layer("Title").x + 40 into a field and press Enter.
Tracker, Mocha	Track tab	Point, Object, Surface (corner pin) or Outline.
3D Camera Tracker	Camera track	Solves the move and the lens, then builds a 3D scene behind your footage.
Rotobrush for "text behind a person"	Depth track + Behind	No masks to paint. More on this below.
Duik, RubberHose	Bones, IK, Character tab	Rigging, poses, blinking and lip sync are built in.
Newton (plugin)	Physics	Gravity, collisions, joints, forces. Built in.
Element 3D, Cinema 4D Lite	3D worlds	Meshes, lights, materials, extruded text, sculpting.
Bodymovin	Lottie export	With a fidelity report of anything that did not translate.
ExtendScript	Scripts panel	Plain JavaScript: await ac.layer.create({…}).

Most of these sit one click away from the layer you selected, in the tabs on the right: Design, Effects, Animate, Track, Physics, Sound.

Is there a graph editor?

Yes. Select a layer, open Curves under the timeline, and every keyed property is drawn as a curve you can shape. Below, a title fades in, drops 100 px and settles from 82% to 100% scale. Three properties, three easings, one view.

Curves: Scale, Y and Opacity keyed on one title, each with its own ease.

Easings have names you can type (ease-out-expo, ease-in-out-back, cubic-bezier(…)), so a curve you liked is a string you can copy into another project. Record mode keys every edit you make while it is on, the way After Effects' stopwatch does once you have clicked it.

Can I write expressions?

Every field that holds a value can hold a formula instead. Click a field, type wiggle(2, 10) or #layer.rotation * 2, press Enter, and it turns purple. Other layers are read by name: layer("Title").x + 40 keeps one layer 40 px to the right of another.

Two details After Effects users tend to like. Expressions are typed (number, vector, colour, text, layer), so a formula that returns the wrong kind of value shows an error while you type, not at render time. And if a formula breaks, the field keeps its last good value and turns red instead of throwing your layer to 0,0.

A tracker is readable the same way: track("Cabin").position is the cabin's position on the current frame. The same values are available on the node board, if you think in wires.

How does tracking work?

Open the Track tab on a video or picture and draw around what you want to follow: a box, an oval, a polygon or a pen outline. It tracks both directions from that frame while you watch the outline ride the footage. Then pick what to do with it: stick a layer on it, stabilize the shot, blur or grade a moving region, or read it in an expression.

The screenshot at the top is that whole loop. The cabin was drawn once on the first frame; the label follows it through the camera move; the Track tab says 97% confidence and lists the label under Used by. When a track drifts, drag the outline back onto the subject on that one frame. The stretch around your fix re-tracks by itself and lands on it, and the fix survives every later re-track.

Trackers belong to the footage, not the clip. Split it, trim it, speed it up, and the track stays glued to the picture. Drop the same file into another project and it is already tracked.

For shots where the camera itself moves, a Camera track solves where the camera went and what lens it used, and Make 3D scene turns that into a 3D world with your footage behind it. Click three points on the floor to level it, then stand a title on a wall or a table and it stays put as the camera moves. It needs real parallax over rigid scenery: a locked-off pan solves as a tripod shot, and a frame full of moving water will not solve.

How do I put text behind a person or a mountain?

In After Effects this is a rotoscoping job: paint a mask on the subject, refine it, fix the frames where it slips. In AtomCut, add a Depth track to the footage. Every pixel gets a distance from the lens, worked out on your own machine (on the GPU when there is one). Then add Behind to the title, and whatever stands in front of it in the shot covers it.

One effect card, Behind, on the title. The peak in front covers the letters; nothing was masked by hand.

The cover of this post is that frame, exported. The same depth drives three more things: Fog that thickens with distance, Lens blur that focuses at a depth (key the focus to rack it), and grade windows that select a band of depth, so you can cool the background and lift the subject without drawing anything.

The depth model downloads once, the first time you use it (60 to 130 MB depending on your machine), and is kept on the device across app updates. After that it works offline. On an M1 MacBook it took about three minutes for an 8-second 1080p clip.

What about characters, physics and 3D?

These are the places where After Effects users usually buy plugins, and where AtomCut ships the feature in the box.

Physics on a title: it falls, lands on the shelf, and the shapes pile up around it. The Physics tab holds body, bounce, friction and forces.

• Physics. Give any layer a body in the Physics tab and it drops, lands and settles. A star lands on its points and a word on its letters. Every frame is a function of time, so you can scrub backwards through a collision.
• Characters. Draw bones through your art, and dragging a hand pulls the arm along (IK). The Character tab holds poses for mouths, eyes, brows and hands. Give a character a voice clip and its mouth follows; fix one syllable by hand and the fix stays.
• 3D worlds. A world is a comp with depth: meshes, lights, materials, extruded text, sculpting and drawing in 3D. It renders on the same timeline as everything else.

A bone with Follow on: the antenna trails the hop and settles by itself. Five frames from a render.

Where is After Effects still the better tool?

Honestly, in several places:

• Heavy footage. A browser tab works within the browser's memory. Long 4K timelines with many layers of video are After Effects (or DaVinci) territory. AtomCut is built for motion graphics, social video and UI animation, not for finishing a feature film.
• The plugin and template ecosystem. Twenty years of Trapcode, Element and marketplace templates do not exist here.
• The pipeline. If your studio hands .aep files around, AtomCut does not open them.
• Tutorials. Every After Effects problem has a ten-year-old YouTube video. AtomCut has its docs and a changelog.

The free editor has every tool, but exports video up to 720p. Full HD and 4K, transparent video and the AI agent link are in Pro: $29 a year with a 7-day free trial, or $59 once for the first 300 buyers.

Can an AI agent drive it?

Yes, and this part has no After Effects equivalent yet. AtomCut speaks MCP, so Claude Code or any MCP client can build scenes, track footage, rig characters and render frames in the editor while you watch, each request one undo step. Every screenshot in this post came out of that same scripting surface: the scenes were built by script in a real editor, then captured. That is a Pro feature; the Scripts panel, where you write the JavaScript yourself, is free.

FAQ

Is AtomCut a free After Effects alternative? The editor is free with no account and no watermark, and exports up to 720p. Pro adds HD and 4K export for $29 a year (7-day free trial) or $59 once.

Does it open After Effects projects? No. It exports MP4, WebM, GIF, PNG sequences, SVG, Lottie and PDF.

Does it work offline? Yes. Once the editor has loaded on a device, it keeps working without a connection, and there are desktop apps for macOS, Windows and Linux.

Can it do motion tracking and text behind a subject? Yes: point, object, surface and outline tracking, a camera solve, and depth-based Behind, Fog and Lens blur. See the tracking docs.

Does it have expressions like After Effects? Yes, in any field, including wiggle(). See expressions and the full capability list.

Open AtomCut in a tab: app.atomcut.net